235/80R16 vs 245/75R16
Going from one to the other changes the overall height by -1.1 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 235/80R16 | 245/75R16 | Change |
|---|---|---|---|
| Overall height | 30.8" | 30.5" | -1.1 % |
| Sidewall | 7.40" | 7.23" | -2.3 % |
| Section width | 235 mm | 245 mm | +4.3 % |
| Circumference | 96.8" | 95.7" | -1.1 % |
| Revs per mile | 655 | 662 | +1.1 % |
| Axle height | 15.40" | 15.23" | -4.3 mm |
| Approved rim width | 6.5–8.5" | 7–9" | overlap 7–8.5" |
Both are approved on a rim 7" to 8.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 235/80R16. Fit 245/75R16 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.7 mph | -0.3 |
| 50 mph | 49.5 mph | -0.5 |
| 70 mph | 69.2 mph | -0.8 |
| 90 mph | 89.0 mph | -1.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,891 on the road, so it over-counts by 109. At a true 70 mph the first turns 764 times a minute, the second 772.